TRENTON, N.J. - Two adults and three juveniles have been charged with gang-raping a 7-year-old girl who was sold by her 15-year-old stepsister during a party at a crime-ridden apartment building, police said Saturday.

Details on the arrests were announced at a Saturday night news conference at police headquarters in Trenton, the state's capital city. The group included a 20-year-old man who already had been charged Friday with having sex with the 15-year-old, and officials said further arrests may be made.

The other four — a 19-year-old Trenton man and three boys ages 13, 14 and 17 — were each charged with aggravated sexual assault and child endangerment.

Authorities say the 7-year-old girl was offered for sale by her 15-year-old stepsister on March 28. They say the teen went to a party with some men on the 13th floor of the Rowan Towers apartment building and the younger girl tagged along because she worried about her stepsister's safety.

Police say the 15-year-old sold sex to men, then took money to let them touch the younger girl. They say touching turned to forcible sex as at least seven men raped the 7-year-old.

Before the arrest announcements, the 15-year-old had been charged with promoting prostitution, aggravated sexual assault and other crimes; police have not released her name, and she remained in juvenile detention Saturday night.